# Google Cloud Storage Reference

> All GCS authentication options and data type handling.

#  Google Cloud Storage Reference

Authentication options and data type handling for [GCS connections](../connect/gcs.md). GCS is accessed through the S3 interoperability layer (`type: s3` with `endpointUrl: https://storage.googleapis.com`).

## Authentication

| Variable | Example | Description |
|---|---|---|
| `DATACONTRACT_S3_ACCESS_KEY_ID` | `GOOG1EZZZ...` | The GCS [HMAC Key](https://cloud.google.com/storage/docs/authentication/hmackeys) ID |
| `DATACONTRACT_S3_SECRET_ACCESS_KEY` | `PDWWpb...` | The GCS [HMAC Key](https://cloud.google.com/storage/docs/authentication/hmackeys) secret |

The `location` in the `servers` block must use the `s3://` scheme (not `gs://`).

## Data types

Same as [Amazon S3](./s3.md#data-types): CSV and JSON files are read as the contract's types (no type checks; JSON additionally validated against a JSON Schema derived from the contract), Parquet and Delta column types are checked against the contract's `logicalType` by category. `physicalType` is never checked against file sources.

{/* AUTOGENERATED TYPE MAPPING: do not edit by hand; regenerate with update_reference_types.py */}

### Logical type mapping

When no `physicalType` is declared, the CLI derives the DuckDB column type from the `logicalType` when reading files. This table is generated from the converters in the CLI's code:

| `logicalType` | CSV read type | Parquet read type |
|---|---|---|
| `string` | `VARCHAR` | `VARCHAR` |
| `integer` | `BIGINT` | `INTEGER` |
| `number` | `DOUBLE` | `DECIMAL` |
| `boolean` | `BOOLEAN` | `BOOLEAN` |
| `date` | `DATE` | `DATE` |
| `timestamp` | `TIMESTAMP` | `TIMESTAMP WITH TIME ZONE` |
| `time` | `TIME` | `TIME` |
| `object` | `VARCHAR` | `STRUCT()` |
| `array` | `VARCHAR` | `VARCHAR[]` |

{/* END AUTOGENERATED TYPE MAPPING */}